Dietmar Keyser

Histological peculiarities of the noding process in Cyprideis torosa (Jones) (Crustacea, Ostracoda)

The noding of Cyprideis torosa is investigated. Studies reveal structural changes in the ornamentation and the cellular layers of the epidermis in the noded area. Noding is caused by the inability of the animal to regulate the increasing osmotic pressure during moulting in low saline water. Therefore it must be considered as a phenotypic and not a genetic response.

Habitat diversity and ostracod distribution patterns in Belarus

Ostracod diversity and abundance was studied in 10 different types of water bodies of Belarus (bogs, brooks, canals, oxbows, ponds, reservoirs, rivers, springs, shoal of lake and temporary pools). Hydrochemical variables, sediment, and vegetation were analyzed. In total 156 different localities were investigated. Habitat diversity was based mainly upon the closely correlated hydrochemical variables of mineralization (hardness total and carbonate, conductivity, total value of dissolved substances), although bottom, vegetation characteristics and other factors (pH, dissolved oxygen, nutrients) were also significant. The ostracods found included 62 species in 27 genera comprising 8 cosmopolitan, 17 Holarctic, 13 Palearctic species; 21 of these species are known from central and southern Europe and adjacent areas, while 3 are characteristic for eastern Europe. The distribution of freshwater ostracod assemblages reflected the habitat and depended on water body type. Heterogeneous oxbows and temporary pools supported 37 species, while other types of pool maintained only 27–14 species. The population density of different species varied from 0.5 to more than 10 000 ind./m2. Indices of local alpha diversity were significantly correlated with the number of species and temperature and were maximal in heterogeneous habitats. The variation of population density was not connected with habitat patterns but appeared to be regulated by the biotic interactions in the community. Habitat diversity, verified by the beta-diversity indices, enabled us to find localities with a similar heterogeneity level and species richness. Beta-diversity values were independent of species number as well as abundance but a significant positive correlation (p < 0.05) was found with temperature, pH and dissolved oxygen. This index probably reflected the general patterns of different localities.

First record of ostracods (Crustacea) in Baltic amber

Ostracods were found in two pieces of Baltic amber for the first time. The animals belong to the freshwater genus Cyclocypris. Since Baltic amber was formed during Eocene times in southern Scandinavia, the age of the specimens is estimated at 42–54 million years. As aquatic organisms, ostracods are seldom trapped in amber; it is considered that one specimen, already dead and dried, was either blown onto sticky resin on a plant stem, or washed there by a high flood level, while the other was probably splashed, alive, in a drop of water against the flowing resin, again probably during a flood. Associated faunal remains, including other crustaceans, suggest a coastal palaeoenvironment with some marine as well as freshwater influence.

Sterilization of contrast media (isovist) containing liposomes by ethylene oxide

Liposomes containing Isovist were prepared by controlled detergent dialysis as well as by reverse phase evaporation. After preparation these liposomes were lyophilized and then submitted to sterilization by ethylene oxide. Prior to lyophilization, trehalose was added as a protective agent to preserve the size of the liposomes. After each step in the preparation size distribution was determined by photon correlation spectroscopy. The computer program CONTIN was adapted for the data analysis and proved to be applicable for polydisperse solutions of liposomes. Neither freeze-drying nor sterilization had negative effects on the morphological quality of the samples when using 4 g of trehalose per 1 g of lipid. In addition, the quality of the liposomes was controlled by scanning electron microscopy. At the end of seven days, no growth of microorganisms occurred in any of the samples.

The shallow marine ostracod communities of the Azores (Mid- North Atlantic): taphonomy and palaeoecology

This is the first palaeoecological and taphonomical study of the Recent marine ostracods from the Azores. The aims of this work were to address the following questions: i) to establish the typical ostracod assemblages from the shallow waters of the Azores; ii) to determine the bathymetric ranges for each ostracod species; iii) to investigate the time span and depth in which significant transport occurs; iv) to quantify the amount of out of habitat transport between sandy beaches, tide pools and the sublittoral; v) to determine distinctive taphonomic features that can be used to recognize the amount of temporal resolution in ostracod assemblages. Fifteen species were recovered, representing 8 families and 12 genera (Loxoconcha, Neonesidea, Xestoleberis, Aurila, Urocythereis, Heterocythereis, Carinocythereis, Callistocythere, Leptocythere, Semicytherura, Lanceostoma and Cylindroleberis). The living assemblages are dominated by specimens of the Loxoconchidae, Xestoleberidae and Hemicytheridae, whereas the dead assemblages are dominated by specimens of the Loxoconchidae, Hemicytheridae, Bairdiidae, Xestoleberidae and Trachyleberidae. The shift from life-dominated assemblages in the shallower depths to death-dominated assemblages at greater depths is a consequence of significant transport downwards. The abundance of ostracods is higher in the first 10-20 m depth, especially in fine to medium sandy substrates. Considerable differences among islands were supported by the Bayesian model, as a consequence of the physical and hydrodynamic factors that differently affect each of the Azorean islands. Large-scale (sea-surface currents, Holocene relative sea-level, storms) and small-scale processes are responsible for shaping the Azorean Recent marine ostracod communities. No living specimens were found in the samples collected at the beach faces, thus reinforcing former interpretations of one of the authors (S. Avila) that advocate that at a global scale, sandy beaches in oceanic islands located at temperate latitudes are almost or even completely devoid of life due to historical reasons related with the sea level changes.

Cuticle Formation of the Adductor Muscle Attachment in a Podocopid Ostracod, as an Example of a Calcified Arthropod

Abstract. The ostracod muscle scars have been used as important characters to define the evolutionary lineages of ostracods from the Palaeozoic to the Recent, though the formation and calcification of their muscle attachment have never been investigated. The present paper describes, for the first time, the cuticle formation of muscle attachment in a podocopid ostracod, as an example of a calcified arthropod. The formation of the muscle attachment structure in a podocopid ostracod progresses through the nearly same pathway as in other arthropods. The muscle connects to the cuticle by means of a specialised epidermal cell, the tendinal cell. Strong desmosomes adhere the muscle cell to the tendinal cell, while the tendinal cell is connected to the cuticle by hemidesmosomes with intracuticular fibres (tonofibrillae). The deposition of the new pre-exuvial cuticle takes place around the extended intracuticular fibres and these fibres maintain the connection between the tendinal cell and the old cuticle. At postecdysis the cuticle of the carapace begins its calcification, and immediately and rapidly increases its thickness, but the calcification of the muscle scars evidently progresses later than other parts of the procuticle, due to the fact that part of the tendinal cell is fully occupied with force-transmitting structures, like microtubules. Only the parts not engaged in force-transmitting action have enough space in the cell to store the granules to start the calcification. Furthermore, the less organic matrix in the procuticle of the muscle attachment area also contributes to the delay of calcification. The results of this paper provide information on cuticle formation in the calcified arthropods, which can be applied to fossil taxa, and show the relationships between the calcified and organic matrix during calcification. In addition, this study suggests that arthropod muscle scars, including in the fossil state, are useful characters when discussing the construction of muscular systems at the cellular level, and available as stable criteria through ontogeny for the comparative morphology of the exoskeleton.

Abundant assemblage of Ostracoda (Crustacea) in Mexican Miocene amber sheds light on the evolution of the brackish-water tribe Thalassocypridini

Abstract Amber inclusions of fully aquatic animals are rare, most of them isolated specimens of water-bound insect larvae. In contrast, we here describe an ample, speciose fauna of 262 fully aquatic individuals of Ostracoda (Crustacea) from Mexican amber of Early Miocene age. This fauna was trapped whilst under water swimming around trunks of resin-producing trees in a brackish lagoon. Ostracod crustaceans are typically around a millimeter in length, and are known for their mostly well-calcified bivalved carapaces that account for their unparalleled fossil record in arthropods. However, in the Chiapas amber we found representatives of the tribe Thalassocypridini, which are characterised by lightly calcified carapaces and therefore lack a substantial fossil record. Embedded in amber, this ‘drawback’ becomes a clear benefit because the unobstructed view onto the appendages otherwise hidden in the carapace allowed us to identify nine ostracod species, six of them new to science. The exceptional number of individuals permitted insights into population composition, reproduction, taphonomy and into micro-environmental parameters of the amber’s place of formation. Based on ecological data available for Recent Thalassocypridini species, we posit that this tribe reached a peak radiation in open lagoonal settings during the Miocene, and shifted towards anchialine environments by the Recent. http://zoobank.org/lsid:zoobank.org:pub:3C93A06B-F86B-404F-985D-139897F97EF3

An exceptionally well preserved new species of ostracod (Crustacea) with soft parts in Baltic amber

Abstract A well-preserved ostracod in Baltic amber has been analysed with noninvasive methods by synchrotron radiation. A micro-tomographic image stack was prepared. The appendages are visualised as images and drawings are based on photographs of different images planes provided. The result is a description of a new species, Cypria kempfi, from the Eocene of Northern Germany. The way the fossilisation of this aquatic animal may have occurred is discussed. The possible ecological preferences of the species are considered.

Morphology and distribution of pelagic ostracods of the genus Boroecia (Ostracoda: Halocyprididae) in the Central Arctic

Morphologically similar Boroecia borealis and B. maxima are redescribed from the Central Arctic. Their morphological differences are minor but well defined. Their geographic and vertical distribution is studied based on an extensive body of materials collected by many expeditions in the Arctic Ocean during the period from 1929 to 1993 at the depth range of 0-4000 m. The comparison of the distribution of both species reveals that B. borealis prefers waters of subarctic structure in the Atlantic, and it inhabits waters in the relatively warm Atlantic layer in the Arctic. In contrast, B. maxima is a good indicator of cool Arctic waters. This species is also present in greater depths of the Northern Atlantic, where polar waters penetrate far towards the south.

Adencythere kodalnamerensis, a new genus and a new species (Ostracoda) from Kod Al-Namer Beach, Aden City, Yemen

A new marine genus of Ostracoda from the tidal flats of Aden City is erected and one new species is described. The systematic position of the present taxon is discussed.